The present invention relates generally to a method and apparatus for sensing an orientation, and more particularly to a viewing method and apparatus for sensing an orientation of a user's head and for viewing and maneuvering in and around a computer generated virtual world.
The use of video displays for recreational, educational, and scientific purposes has increased dramatically in recent years. Video displays are commonly used in medical operations, for example, and in many other analytical fields to visually present a simulated environment to a user. Another particular application is in the video game industry where video displays transmit real time image data to a user. The video display is programmed to respond to actions taken by the user through a control mechanism such as a joy stick and is updated in real time.
Recently, video displays have been adapted to be secured a fixed distance in front of the user's eyes and to provide real time image data based on, for example, the movement of the user's head. Commonly known as "virtual reality", a motion sensor senses movement of the user's head and provides a signal representing the motion to a microprocessor which calculates the real time image data based on the signal.
In many known systems, the video display is fixed inside a helmet which the user wears while using the apparatus. U.S. Pat. No. 4,884,219, for example, discloses an apparatus for the perception of computer-generated imagery comprising a helmet which includes two visual display units and a first module containing three small coils. A second module also having three small coils is fixed at a location remote from the helmet. The second module acts as a transmitter to generate a low frequency electric field. The first module acts as a moveable sensor which samples the field generated by the second module. An electronics decode circuit decodes a signal from the first module and computes the sensor's position and orientation in angular coordinates.
Although this helmet-type apparatus may be used to sense an orientation of the user's head and to calculate image data, it has several disadvantages. For example, people who use the apparatus will have different sized heads. The helmet, therefore, will typically have to include a relatively complex mechanism for allowing a size adjustment of the helmet before each person uses the apparatus. It is usually necessary, therefore, to hire an attendant to assist users in fitting the helmet to the user's head, which has obvious cost disadvantages. Each fitting may also take an undesirably long period of time, which significantly curtails receipts, and which may deter potential users from waiting in line to use the apparatus.
In addition, the use of the same helmet by all users may cause problems with respect to hygiene, which may deter a significant number of potential user's from using the apparatus. Moreover, because the helmet is not supported other than by resting on the user's head, the mass of the helmet must be kept at a reasonable mass, which may significantly affect the quality and size of the visual display units which can be used.
In other known systems, a visual display is suspended from a boom which may be counterbalanced such that the visual display does not weigh down on the user's head. U.S. Pat. No. 5,253,832, for example, discloses a spring counterbalanced boom suspension system in which the visual display is suspended from a boom arm which is rotatably connected to a cantilever arm. In this system, however, the freedom of motion of the visual display is substantially more limited than in the helmet-type apparatus of the above-cited U.S. Pat. No. 4,884,219. For example, the visual display can rotate only about two axes with respect to the boom arm which supports it. Also, the apparatus is designed to be lightweight, which may significantly limit the size and quality of the LCD units which may be used in the visual display. In addition, the use of springs for counterbalancing cannot provide the precision of using counterweights, since the spring constant is not easily adjusted and may vary somewhat as the spring is expanded or contracted.
It would be desirable, therefore, to have a viewing apparatus which provides image data to a user based on the movement of the user's head, which can be used by any user without a significant setup time, which supports relatively large LCD displays, which allows a high degree of rotational freedom, and which can be left unattended without risk of damage to the apparatus.